Can’t Shake This Feeling

The data provided do not identify a unifying diagnosis. To look for an inflammatory myopathy, such as dermatomyositis or polymyositis, it is reasonable to perform electromyography (EMG) to delineate the location of muscle involvement and identify a site for tissue biopsy. As no obvious toxins or metabolic conditions explain the dysmetria, magnetic resonance imaging (MRI) of the brain should be performed to evaluate for lesions in the cerebellum.

The patient was admitted to the hospital. On T2-weighted and FLAIR (fluid attenuation inversion recovery) sequences, MRI of the brain showed a few scattered subcortical and periventricular white matter hyperintense foci bilaterally. Antibodies to human immunodeficiency virus 1 and 2, and Treponema pallidum immunoglobulins G and M, were not detected. Serum levels of lactate dehydrogenase, vitamin B ₁₂ , angiotensin-converting enzyme, antinuclear antibody, rheumatoid factor, and anti–cyclic citrullinated peptide IgG were normal.

The brain imaging excludes a space-occupying lesion in the cerebellum but does not identify the cause of dysmetria. Toxic-metabolic conditions, such as alcohol toxicity, vitamin B₁₂ deficiency, anoxia, and toxicity of certain medications, may impair cerebellar function (MRI findings may be normal), but none of these is present. Other disorders that attack the central nervous system (CNS) (again, brain imaging may show minimal abnormalities) include infections, early-stage neurodegenerative illnesses, and antibody-associated disorders (eg, autoimmune diseases, postinfectious and paraneoplastic conditions).

Four days after intravenous fluids were started, the patient’s CK level improved, but her weakness persisted. There was no evidence of peripheral neuropathy on lower extremity nerve conduction studies. EMG revealed few fibrillations and positive sharp waves in proximal limb muscles and thoracic paraspinal muscles. Deltoid, biceps, and tensor fasciae latae showed shorter duration complex motor units with early recruitment. The patient declined muscle biopsy. A rheumatologist was consulted, and prednisone 60 mg/d was started for possible inflammatory myopathy. The patient was discharged to a skilled nursing facility for physical therapy.

The fibrillations and positive sharp waves on EMG can be seen in both neuropathy (from denervation) and myopathy. The normal nerve conduction studies make localization to the nerve unlikely. In addition, the shorter duration motor units with early recruitment on EMG are characteristic of a myopathy. Despite the ongoing myopathy, the improved CK level suggests the muscle disease is playing a minimal role in the patient’s current illness. Prescribing corticosteroids for a presumed inflammatory myopathy without a clear diagnosis is risky, as steroids may render subsequent biopsy results unreliable, may themselves cause myopathy, and expose the patient to the side effects of immunosuppression.

One month later, the patient saw her rheumatologist. Although she had tapered the prednisone down to 10 mg/d, she had not returned to baseline strength, was still using a walker, and reported increased difficulty keeping her head raised. She also noted 2 new symptoms: speech slurring and, in both hands, a tremor that made it difficult to hold objects.

Examination revealed a fine tremor in both arms. There were no skin lesions, and the joints were normal. The patient was oriented to name, place, and date. Memory testing was 3 for 3 on register but 0 for 3 on recall. She was unable to perform serial 7s and able to spell backward only 3 of the 5 letters in the word world . Speech was dysarthric and scanning in quality. On extraocular movements, she demonstrated poor smooth pursuit. Examination of the head and neck was significant for nearly constant head titubation and weak neck flexors. Upper extremity strength was normal. Mild weakness was noted in both hip flexors. Deep tendon reflexes were preserved except at the ankle, where they were reduced. Finger–nose–finger testing revealed marked dysmetria, more pronounced on the left, and there was mild bilateral heel-to-shin dysmetria.

Diffuse myopathy cannot account for the patient’s impaired cognition or progressive cerebellar findings, which now include head titubation and scanning speech. As more than a month has elapsed since the brain imaging was performed, MRI could be repeated for evidence of infection, malignancy, inflammation, or demyelination. More important, lumbar puncture is indicated to exclude infection and, with flow cytometry, cytology, and measurement of oligoclonal bands and IgG index, to assess for autoimmune or paraneoplastic antibody-mediated disorders.

The patient was readmitted. On repeat brain MRI, there were no new significant findings. Complete blood cell count and chemistry panel results were unremarkable. Erythrocyte sedimentation rate and C-reactive protein level remained normal. CK level was 451 U/L, and ALT level 29 U/L.